Alkylene oxides such as propylene oxide are important materials of commerce. Processes for the preparation of the alkylene oxides include the chlorohydrin process as well as the hydroperoxide route; see, for example, U.S. Pat. No. 3,351,635. Because the chlorohydrin process is costly and produces polluting byproducts and the hydroperoxide process produces a coproduct such as styrene or TBA, the industry has sought an improved direct oxidation process for alkylene oxide production.
One such improved process is the production of propylene oxide by reaction of propylene, oxygen and hydrogen in the presence of an appropriate catalyst or mixture of catalysts. See for example, Japanese Kokai No. 4-352771, JP H8-269029, JP H8-269030, U.S. Pat. No. 6,005,123, U.S. Pat. No. 6,005,123, U.S. Pat. No. 6,498,259 and the like, the disclosures of which are incorporated herein by reference. A useful description of the production of propylene oxide by reaction of propylene, oxygen and hydrogen in a salt buffered system is found in U.S. Pat. No. 6,498,259.
In such systems, the recovery and recycle of buffer salts is of considerable importance insofar as the overall economics of the process is concerned.